Van den Koornhuyse N, Libessart N, Delrue B, Zabawinski C, Decq A, Iglesias A, Carton A, Preiss J, Ball S
Laboratoire de Chimie Biologique, Unité Mixte de Recherche du CNRS 111, Université des Sciences et Techniques de Lille Flandres-Artois 59655 Villeneuve d'Ascq Cedex, France 59655.
J Biol Chem. 1996 Jul 5;271(27):16281-7. doi: 10.1074/jbc.271.27.16281.
In Chlamydomonas, as in higher plants, synthesis of ADP glucose catalyzed by ADP-glucose pyrophosphorylase is rate-limiting for the building of starch in the chloroplast. We have isolated disruptions of the STA1 ADP-glucose pyrophosphorylase structural gene that rendered the enzyme less responsive to the allosteric activator 3-phosphoglycerate. The structure and composition of the residual starch synthesized by all mutants of the STA1 locus is dramatically altered. The residual polysaccharide is shown to be devoid of amylose despite the presence of granule-bound starch synthase, the amylose biosynthetic enzyme. In addition, the fine structure of the mutant amylopectin revealed the presence of an altered chain-length distribution. This distribution mimicks that which is observed during growth and photosynthesis and differs markedly from that observed during storage. We therefore propose that low nucleotide sugar concentrations are either directly or indirectly responsible for the major differences observed in the composition or structure of starch during storage and photosynthesis.
与高等植物一样，衣藻中由ADP - 葡萄糖焦磷酸化酶催化合成ADP葡萄糖是叶绿体中淀粉合成的限速步骤。我们分离出了STA1 ADP - 葡萄糖焦磷酸化酶结构基因的缺失突变体，该突变使酶对变构激活剂3 - 磷酸甘油酸的反应性降低。由STA1位点的所有突变体合成的残留淀粉的结构和组成发生了显著改变。尽管存在颗粒结合淀粉合酶（直链淀粉生物合成酶），但残留多糖显示不含直链淀粉。此外，突变支链淀粉的精细结构显示出链长分布发生了改变。这种分布类似于在生长和光合作用期间观察到的分布，与在储存期间观察到的分布明显不同。因此，我们提出低核苷酸糖浓度直接或间接导致了在储存和光合作用期间淀粉的组成或结构中观察到的主要差异。
